The 2013 Montana legislature passed a new law that made child endangerment a felony crime.

That law was applied Wednesday, when Theresa Birdsley, 22, was arrested for allegedly driving drunk with a child in the vehicle. Deputy Missoula County Attorney Jordan Kilby explains why the law was applied in this case.

"Ms. Birdsley is being charged with criminal child endangerment," Kilby said. "Essentially, what that is person who is driving under the influence of alcohol with a child who is under 14 years old."

"She was pulled over at about 2:45 Wednesday morning, and she had a child, I believe it was under two in the vehicle, and she was cited for DUI, then we took the case and charged her with criminal child endangerment," Kilby said.